1. Field of the Invention
This invention relates to an unvulcanized rubber mixture, which contains an unvulcanized rubber, aggregate, and at least one filler.
2. Discussion of Background
In an unvulcanized rubber mixture, the fillers have significant importance. Not only do they contribute to the cost reduction of unvulcanized rubber mixtures, but their specific effects upon the unvulcanized rubber are utilized. In the field of unvulcanized rubber, one differentiates the fillers according to the distinctiveness of their effect (activity). The activity of a filler is dependent upon its particle size, its specific surface, its geometric shape, and its chemical composition. Thus, one characterizes fillers as active (reinforcing fillers), in which a characteristic optimum is noted in relation to its concentration, such that this unvulcanized rubber feature is "actively" influenced. For example, carbon black and silicic acid are included among these fillers. In contrast to the reinforcing fillers, an almost exclusively constant alteration of the feature image can be observed in the inactive fillers (reinforcing only via volume content), with the degree of the filler. For example, chalk may be used as an inactive filler in unvulcanized rubber mixtures.
As already mentioned, the activity of a filler is dependent upon the particle size, the specific surface, the geometric form of the particle, and its chemical structure. The reinforcing effect is essentially based upon physical and/or chemical reciprocal actions at the border between the filler and the unvulcanized rubber matrix. The surface characteristics of the fillers especially play a significant role. It is, for example, known to modify the surface of silicic acid with a hydrosilicon, in order to produce a good bond to the unvulcanized rubber matrix and thus to influence positively the characteristics of the vulcanized material. Such measures are known, for example, for the production of treads for vehicle pneumatic tires, which give the vehicle pneumatic tires a low rolling friction and a good wet skidding performance. However, such interactions between filler and unvulcanized rubber matrix are based upon a one-time, irreversible coupling process during the manufacture of the vulcanized material. If, however, the atmospheric temperature or the load condition of the vulcanized material changes, for example, a filler which is bound in the conventional way to the matrix is no longer in a position to react to these influences, in order to ensure sufficient dynamic-mechanical characteristics, for example, when the vulcanized material is being used.